Dearborn — Lecturers at the University of Michigan are calling on school officials to raise their wages, saying they have been underpaid for years and threaten to go on strike if the school rejects their request. The Lecturers’ Employee Organization — which represents 1,700 non-tenure lecturers at the Ann Arbor, Dearborn and Flint campuses — says it has been bargaining for a new contract with the university since October, and its contract expires May 29. The union members gathered at the Dearborn campus on Thursday to display unity before going to the University of Michigan Board of Regents’ meeting to speak out. Union leaders say many lecturers on all three campuses are not making enough to support a family and have to work additional jobs for more income. They also want equal pay rates at all three campuses. Ann Arbor lecturers are paid higher salaries.